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Rh operations, until it was again revised under date of September 15, 1939, by issuance of a new map entitled “Highway map showing main traffic routes of military importance.”

Shortly thereafter, at the suggestion of the War Department, the Public Roads Administration undertook, with the aid of the highway planning surveys of the States, a study of the condition of existing roads conforming closely to the routes shown on this latest revision of the map. The feasibility and general adequacy of the indicated network also were carefully weighed, following which the Public Roads Administration prepared and submitted to the War Department for its consideration a further revision of the map.

With a few additional changes, this revised map was endorsed by the Secretary of War on November 20, 1940, as representing the principal routes of military importance. With further slight amendments by the Navy Department, it is included as plate 1 in this report. It is still subject, however, to further amendment by the deletion or addition of routes and the revision of general directions, as studies still in progress show this to be advisable.

As viewed by the War and Navy Departments, this map is considered to represent a system of general routes. No precise definition is given of the location of roads comprising the routes between major “controlling points,” which generally are large cities. In fact, in its broadest conception, the network consists not of a single road between each of the controlling points, but rather of a main line and approximately parallel auxiliary lines, with suitable connections between them at frequent intervals. The purposes of the auxiliary lines are: (1) To permit, if necessary, a division of traffic, especially military convoy movements, among at least three roads between any points, and (2) to provide alternate routes for use in case of obstruction of the main road by any cause.

The main lines of the network, as now approved by the War and Navy Departments, include all sections of the interregional highway system recommended by the Public Roads Administration in the report, Toll Roads and Free Roads. With few exceptions they are also in close conformity with roads included in the Federal-aid highway system.

While all of the routes designated are considered important to the national defense, an order of relative importance within the network is indicated by classification of the routes into first, second, and third priorities. The approximate extent of the main lines of the network is 74,600 miles, composed of about 42,400 miles of first priority, 23,100 miles of second priority, and 9,100 miles of third priority.

EXTENT AND CHARACTER OF IMPROVEMENTS REQUIRED ON THE STRATEGIC NETWORK Existing roads and streets conforming most closely to the main lines of the strategic network total 74,626 miles. Of this total, 66,869 miles consist of rural highways, 7,757 miles of highways and streets in cities. Routes designated as of first priority total 42,422 miles. Of this mileage 29,331 miles consist of routes included in the interregional system recommended by the Public Roads Administration